U.S. patent application number 14/716104 was filed with the patent office on 2015-12-17 for hvac system mode detection based on control line current.
This patent application is currently assigned to EMERSON ELECTRIC CO.. The applicant listed for this patent is EMERSON ELECTRIC CO.. Invention is credited to Priotomo ABIPROJO, Jeffrey N. ARENSMEIER.
Application Number | 20150362207 14/716104 |
Document ID | / |
Family ID | 54834449 |
Filed Date | 2015-12-17 |
United States Patent
Application |
20150362207 |
Kind Code |
A1 |
ABIPROJO; Priotomo ; et
al. |
December 17, 2015 |
HVAC System Mode Detection Based On Control Line Current
Abstract
A monitoring system for monitoring a heating, ventilation, and
air conditioning (HVAC) system of a building includes a monitoring
server. The monitoring server is configured to receive an aggregate
control line current value from a monitoring device. The aggregate
control line current value represents a total current flowing
through control lines used by a thermostat to command the HVAC
system. The monitoring server is configured to determine a
commanded operating mode of the HVAC system in response to the
aggregate control line current value. Operating modes of the HVAC
system include at least one of an idle mode and an ON mode. The
monitoring server is configured to analyze a system condition of
the HVAC system based on the determined commanded operating
mode.
Inventors: |
ABIPROJO; Priotomo;
(O'Fallon, MO) ; ARENSMEIER; Jeffrey N.; (Fenton,
MO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EMERSON ELECTRIC CO. |
St. Louis |
MO |
US |
|
|
Assignee: |
EMERSON ELECTRIC CO.
St. Louis
MO
|
Family ID: |
54834449 |
Appl. No.: |
14/716104 |
Filed: |
May 19, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62011471 |
Jun 12, 2014 |
|
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|
Current U.S.
Class: |
702/183 |
Current CPC
Class: |
F24F 11/32 20180101;
F24F 11/52 20180101; F24F 2110/00 20180101; F24F 11/30 20180101;
F24F 11/56 20180101; F24F 11/63 20180101; F24F 2140/50 20180101;
F24F 11/62 20180101 |
International
Class: |
F24F 11/00 20060101
F24F011/00 |
Claims
1. A monitoring system for monitoring a heating, ventilation, and
air conditioning (HVAC) system of a building, the monitoring system
comprising: a monitoring server configured to: receive an aggregate
control line current value from a monitoring device, wherein the
aggregate control line current value represents a total current
flowing through control lines used by a thermostat to command the
HVAC system; determine a commanded operating mode of the HVAC
system in response to the aggregate control line current value,
wherein operating modes of the HVAC system include at least one of
an idle mode and an ON mode; and analyze a system condition of the
HVAC system based on the determined commanded operating mode.
2. The monitoring system of claim 1 wherein the system condition
includes at least one of a detected fault of the HVAC system and a
predicted fault of the HVAC system.
3. The monitoring system of claim 2 wherein the monitoring server
is configured to generate an alert for at least one of a customer
and a contractor in response to determining presence of at least
one of the detected fault and the predicted fault.
4. The monitoring system of claim 1 wherein the monitoring server
is located remotely from the building.
5. The monitoring system of claim 1 further comprising the
monitoring device, wherein the monitoring device is installed at
the building, and wherein the monitoring device is configured to
measure the total current flowing through the control lines.
6. The monitoring system of claim 5 wherein the monitoring device
includes a current sensor that measures a first current flowing
through a conductor supplying power to the thermostat, wherein the
monitoring device determines the aggregate control line current
value based on the first current.
7. The monitoring system of claim 5 wherein: the monitoring device
includes a voltage sensor that measures a voltage on an output side
of a transformer associated with the control lines, the monitoring
device determines the aggregate control line current based on an
apparent transformer ratio, and the apparent transformer ratio is
based on the measured voltage of the output side of the transformer
and a voltage on an input side of the transformer.
8. The monitoring system of claim 5 wherein the monitoring device
includes a voltage sensor that measures a voltage associated with
the control lines, and wherein the monitoring device determines the
aggregate control line current based on the measured voltage.
9. The monitoring system of claim 5 further comprising a second
monitoring device, wherein: the second monitoring device includes a
current sensor configured to measure an aggregate control line
current consumed by an outdoor unit of the HVAC system; and the
monitoring server is configured to infer, in response to the
commanded operating mode of the HVAC system being unknown, the
commanded operating mode using the aggregate control line current
consumed by the outdoor unit.
10. The monitoring system of claim 1 wherein the ON mode
encompasses a plurality of operating modes including at least two
of the following: a fan only mode, a heating mode, a second stage
heating mode, a cooling mode, a second stage cooling mode, an
auxiliary heating mode, and an emergency mode.
11. The monitoring system of claim 1 wherein the monitoring server
is configured to: store a table of aggregate control line current
values with respect to the operating modes of the HVAC system; and
determine the commanded operating mode of the HVAC system based on
the table.
12. The monitoring system of claim 11 wherein the table includes an
aggregate control line current value corresponding to each of the
operating modes of the HVAC system.
13. The monitoring system of claim 12 wherein: a first current
value is associated with a first upper limit and a first lower
limit in the table and corresponds to a first operating mode; and
the monitoring server is configured to determine that the commanded
operating mode of the HVAC system is the first operating mode in
response to the received aggregate control line current being
greater than or equal to the first lower limit and less than or
equal to the first upper limit.
14. The monitoring system of claim 11 wherein the table is
predefined upon commissioning of the HVAC system.
15. The monitoring system of claim 11 wherein the table is
predefined based on a model number of the HVAC system.
16. The monitoring system of claim 11 wherein the monitoring server
is configured to populate the table.
17. The monitoring system of claim 1 wherein the monitoring server
is configured to, in response to the commanded operating mode of
the HVAC system being unknown, infer the commanded operating mode
using additional data.
18. The monitoring system of claim 17 wherein the monitoring server
is configured to store the inference along with the received
aggregate control line current for future use.
19. The monitoring system of claim 17 wherein the additional data
includes outside ambient temperature in a geographical region of
the HVAC system.
20. The monitoring system of claim 17 wherein the additional data
includes supply air temperature of the HVAC system.
21. The monitoring system of claim 17 wherein the additional data
includes a refrigerant line temperature of the HVAC system.
22. The monitoring system of claim 17 wherein the additional data
includes a time of year.
23. The monitoring system of claim 17 wherein the additional data
includes an aggregate current consumption of the HVAC system.
24. The monitoring system of claim 23 wherein the aggregate current
consumption of the HVAC system includes all current drawn by
components of either (i) an indoor enclosure of the HVAC system or
(ii) an outdoor enclosure of the HVAC system.
25. The monitoring system of claim 24 wherein the additional data
includes at least one of: a steady-state value of the aggregate
current consumed by the indoor enclosure; and a time-domain or
frequency-domain signature of the aggregate current consumed by the
indoor enclosure.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/011,471, filed on Jun. 12, 2014. The entire
disclosure of the application referenced above is incorporated
herein by reference.
FIELD
[0002] The present disclosure relates to environmental comfort
systems and more particularly to remote monitoring and diagnosis of
residential and light commercial environmental comfort systems.
BACKGROUND
[0003] The background description provided herein is for the
purpose of generally presenting the context of the disclosure. Work
of the presently named inventors, to the extent it is described in
this background section, as well as aspects of the description that
may not otherwise qualify as prior art at the time of filing, are
neither expressly nor impliedly admitted as prior art against the
present disclosure.
[0004] A residential or light commercial HVAC (heating,
ventilation, or air conditioning) system controls environmental
parameters, such as temperature and humidity, of a building. The
target values for the environmental parameters, such as a
temperature set point, may be specified by a user or owner of the
building, such as an employee working in the building or a
homeowner.
[0005] In FIG. 1, a block diagram of an example HVAC system is
presented. In this particular example, a forced air system with a
gas furnace is shown. Return air is pulled from the building
through a filter 104 by a circulator blower 108. The circulator
blower 108, also referred to as a fan, is controlled by a control
module 112. The control module 112 receives signals from a
thermostat 116. For example only, the thermostat 116 may include
one or more temperature set points specified by the user.
[0006] The thermostat 116 may direct that the circulator blower 108
be turned on at all times or only when a heat request or cool
request is present (automatic fan mode). In various
implementations, the circulator blower 108 can operate at multiple
speeds or at any speed within a predetermined range. One or more
switching relays (not shown) may be used to control the circulator
blower 108 and/or to select a speed of the circulator blower
108.
[0007] The thermostat 116 provides the heat and/or cool requests to
the control module 112. When a heat request is made, the control
module 112 causes a burner 120 to ignite. Heat from combustion is
introduced to the return air provided by the circulator blower 108
in a heat exchanger 124. The heated air is supplied to the building
and is referred to as supply air.
[0008] The burner 120 may include a pilot light, which is a small
constant flame for igniting the primary flame in the burner 120.
Alternatively, an intermittent pilot may be used in which a small
flame is first lit prior to igniting the primary flame in the
burner 120. A sparker may be used for an intermittent pilot
implementation or for direct burner ignition. Another ignition
option includes a hot surface igniter, which heats a surface to a
high enough temperature that, when gas is introduced, the heated
surface initiates combustion of the gas. Fuel for combustion, such
as natural gas, may be provided by a gas valve 128.
[0009] The products of combustion are exhausted outside of the
building, and an inducer blower 132 may be turned on prior to
ignition of the burner 120. In a high efficiency furnace, the
products of combustion may not be hot enough to have sufficient
buoyancy to exhaust via conduction. Therefore, the inducer blower
132 creates a draft to exhaust the products of combustion. The
inducer blower 132 may remain running while the burner 120 is
operating. In addition, the inducer blower 132 may continue running
for a set period of time after the burner 120 turns off.
[0010] A single enclosure, which will be referred to as an air
handler unit 136, may include the filter 104, the circulator blower
108, the control module 112, the burner 120, the heat exchanger
124, the inducer blower 132, an expansion valve 140, an evaporator
144, and a condensate pan 146. In various implementations, the air
handler unit 136 includes an electrical heating device (not shown)
instead of or in addition to the burner 120. When used in addition
to the burner 120, the electrical heating device may provide backup
or secondary heat.
[0011] In FIG. 1, the HVAC system includes a split air conditioning
system. Refrigerant is circulated through a compressor 148, a
condenser 152, the expansion valve 140, and the evaporator 144. The
evaporator 144 is placed in series with the supply air so that when
cooling is desired, the evaporator 144 removes heat from the supply
air, thereby cooling the supply air. During cooling, the evaporator
144 is cold, which causes water vapor to condense. This water vapor
is collected in the condensate pan 146, which drains or is pumped
out.
[0012] A control module 156 receives a cool request from the
control module 112 and controls the compressor 148 accordingly. The
control module 156 also controls a condenser fan 160, which
increases heat exchange between the condenser 152 and outside air.
In such a split system, the compressor 148, the condenser 152, the
control module 156, and the condenser fan 160 are generally located
outside of the building, often in a single condensing unit 164.
[0013] In various implementations, the control module 156 may
simply include a run capacitor, a start capacitor, and a contactor
or relay. In fact, in certain implementations, the start capacitor
may be omitted, such as when a scroll compressor instead of a
reciprocating compressor is being used. The compressor 148 may be a
variable-capacity compressor and may respond to a multiple-level
cool request. For example, the cool request may indicate a
mid-capacity call for cool or a high-capacity call for cool.
[0014] The electrical lines provided to the condensing unit 164 may
include a 240 volt mains power line (not shown) and a 24 volt
switched control line. The 24 volt control line may correspond to
the cool request shown in FIG. 1. The 24 volt control line controls
operation of the contactor. When the control line indicates that
the compressor should be on, the contactor contacts close,
connecting the 240 volt power supply to the compressor 148. In
addition, the contactor may connect the 240 volt power supply to
the condenser fan 160. In various implementations, such as when the
condensing unit 164 is located in the ground as part of a
geothermal system, the condenser fan 160 may be omitted. When the
240 volt mains power supply arrives in two legs, as is common in
the U.S., the contactor may have two sets of contacts, and can be
referred to as a double-pole single-throw switch.
[0015] Monitoring of operation of components in the condensing unit
164 and the air handler unit 136 has traditionally been performed
by an expensive array of multiple discrete sensors that measure
current individually for each component. For example, a first
sensor may sense the current drawn by a motor, another sensor
measures resistance or current flow of an igniter, and yet another
sensor monitors a state of a gas valve. However, the cost of these
sensors and the time required for installation of, and taking
readings from, the sensors has made monitoring
cost-prohibitive.
SUMMARY
[0016] A monitoring system for monitoring a heating, ventilation,
and air conditioning (HVAC) system of a building includes a
monitoring server. The monitoring server is configured to receive
an aggregate control line current value from a monitoring device.
The aggregate control line current value represents a total current
flowing through control lines used by a thermostat to command the
HVAC system. The monitoring server is configured to determine a
commanded operating mode of the HVAC system in response to the
aggregate control line current value. Operating modes of the HVAC
system include at least one of an idle mode and an ON mode. The
monitoring server is configured to analyze a system condition of
the HVAC system based on the determined commanded operating
mode.
[0017] In other features, the system condition includes at least
one of a detected fault of the HVAC system and a predicted fault of
the HVAC system. In other features, the monitoring server is
configured to generate an alert for at least one of a customer and
a contractor in response to determining presence of at least one of
the detected fault and the predicted fault. In other features, the
monitoring server is located remotely from the building. In other
features, the monitoring device is installed at the building. The
monitoring device is configured to measure the total current
flowing through the control lines.
[0018] In other features, the monitoring device includes a current
sensor that measures a first current flowing through a conductor
supplying power to the thermostat. The monitoring device determines
the aggregate control line current value based on the first
current. In other features, the monitoring device includes a
voltage sensor that measures a voltage on an output side of a
transformer associated with the control lines. The monitoring
device determines the aggregate control line current based on an
apparent transformer ratio. The apparent transformer ratio is based
on the measured voltage of the output side of the transformer and a
voltage on an input side of the transformer.
[0019] In other features, the monitoring device includes a voltage
sensor that measures a voltage associated with the control lines.
The monitoring device determines the aggregate control line current
based on the measured voltage. In other features, the system
includes a second monitoring device. The second monitoring device
includes a current sensor configured to measure an aggregate
control line current consumed by an outdoor unit of the HVAC
system. The monitoring server is configured to infer, in response
to the commanded operating mode of the HVAC system being unknown,
the commanded operating mode using the aggregate control line
current consumed by the outdoor unit.
[0020] In other features, the ON mode encompasses multiple
operating modes including at least two of the following: a fan only
mode, a heating mode, a second stage heating mode, a cooling mode,
a second stage cooling mode, an auxiliary heating mode, and an
emergency mode. In other features, the monitoring server is
configured to store a table of aggregate control line current
values with respect to the operating modes of the HVAC system. The
monitoring server is configured to determine the commanded
operating mode of the HVAC system based on the table. In other
features, the table includes an aggregate control line current
value corresponding to each of the operating modes of the HVAC
system.
[0021] In other features, a first current value is associated with
a first upper limit and a first lower limit in the table and
corresponds to a first operating mode. The monitoring server is
configured to determine that the commanded operating mode of the
HVAC system is the first operating mode in response to the received
aggregate control line current being greater than or equal to the
first lower limit and less than or equal to the first upper limit.
In other features, the table is predefined upon commissioning of
the HVAC system. In other features, the table is predefined based
on a model number of the HVAC system. In other features, the
monitoring server is configured to populate the table.
[0022] In other features, the monitoring server is configured to,
in response to the commanded operating mode of the HVAC system
being unknown, infer the commanded operating mode using additional
data. In other features, the monitoring server is configured to
store the inference along with the received aggregate control line
current for future use. In other features, the additional data
includes outside ambient temperature in a geographical region of
the HVAC system. In other features, the additional data includes
supply air temperature of the HVAC system. In other features, the
additional data includes a refrigerant line temperature of the HVAC
system.
[0023] In other features, the additional data includes a time of
year. In other features, the additional data includes an aggregate
current consumption of the HVAC system. In other features, the
aggregate current consumption of the HVAC system includes all
current drawn by components of either (i) an indoor enclosure of
the HVAC system or (ii) an outdoor enclosure of the HVAC system. In
other features, the additional data includes at least one of (i) a
steady-state value of the aggregate current consumed by the indoor
enclosure, and (ii) a time-domain or frequency-domain signature of
the aggregate current consumed by the indoor enclosure.
[0024] A method of operating a monitoring system for a heating,
ventilation, and air conditioning (HVAC) system of a building
includes receiving an aggregate control line current value from a
monitoring device. The aggregate control line current value
represents a total current flowing through control lines used by a
thermostat to command the HVAC system. The method includes
determining a commanded operating mode of the HVAC system in
response to the aggregate control line current value. Operating
modes of the HVAC system include at least one of an idle mode and
an ON mode. The method includes analyzing a system condition of the
HVAC system based on the determined commanded operating mode.
[0025] In other features, the system condition includes at least
one of a detected fault of the HVAC system and a predicted fault of
the HVAC system. In other features, the method includes generating
an alert for at least one of a customer and a contractor in
response to determining presence of at least one of the detected
fault and the predicted fault. In other features, the monitoring
server is located remotely from the building.
[0026] In other features, the monitoring device is installed at the
building. The method further includes measuring the total current
flowing through the control lines using the monitoring device. In
other features, the monitoring device includes a current sensor
that measures a first current flowing through a conductor supplying
power to the thermostat. The method further includes determining
the aggregate control line current value based on the first
current.
[0027] In other features, the monitoring device includes a voltage
sensor that measures a voltage on an output side of a transformer
associated with the control lines. The method further includes (i)
determining an apparent transformer ratio based on the measured
voltage of the output side of the transformer and a voltage on an
input side of the transformer and (ii) determining the aggregate
control line current based on the apparent transformer ratio. In
other features, the monitoring device includes a voltage sensor
that measures a voltage associated with the control lines. The
method further includes determining the aggregate control line
current based on the measured voltage.
[0028] In other features, the method includes measuring an
aggregate control line current consumed by an outdoor unit of the
HVAC system using a second monitoring device that includes a
current sensor. The method includes, in response to the commanded
operating mode of the HVAC system being unknown, inferring the
commanded operating mode using the aggregate control line current
consumed by the outdoor unit. In other features, the ON mode
encompasses multiple operating modes including at least two of the
following: a fan only mode, a heating mode, a second stage heating
mode, a cooling mode, a second stage cooling mode, an auxiliary
heating mode, and an emergency mode.
[0029] In other features, the method includes storing a table of
aggregate control line current values with respect to the operating
modes of the HVAC system, and determining the commanded operating
mode of the HVAC system based on the table. In other features, the
table includes an aggregate control line current value
corresponding to each of the operating modes of the HVAC
system.
[0030] In other features, a first current value is associated with
a first upper limit and a first lower limit in the table and
corresponds to a first operating mode. The method further includes
determining that the commanded operating mode of the HVAC system is
the first operating mode in response to the received aggregate
control line current being greater than or equal to the first lower
limit and less than or equal to the first upper limit.
[0031] In other features, the table is predefined upon
commissioning of the HVAC system. In other features, the table is
predefined based on a model number of the HVAC system. In other
features, the method includes populating the table. In other
features, the method includes, in response to the commanded
operating mode of the HVAC system being unknown, inferring the
commanded operating mode using additional data.
[0032] In other features, the method includes storing the inference
along with the received aggregate control line current for future
use. In other features, the additional data includes outside
ambient temperature in a geographical region of the HVAC system. In
other features, the additional data includes supply air temperature
of the HVAC system. In other features, the additional data includes
a refrigerant line temperature of the HVAC system. In other
features, the additional data includes a time of year.
[0033] In other features, the additional data includes an aggregate
current consumption of the HVAC system. In other features, the
aggregate current consumption of the HVAC system includes all
current drawn by components of either (i) an indoor enclosure of
the HVAC system or (ii) an outdoor enclosure of the HVAC system. In
other features, the additional data includes at least one of (i) a
steady-state value of the aggregate current consumed by the indoor
enclosure, and (ii) a time-domain or frequency-domain signature of
the aggregate current consumed by the indoor enclosure.
[0034] Further areas of applicability of the present disclosure
will become apparent from the detailed description, the claims and
the drawings. The detailed description and specific examples are
intended for purposes of illustration only and are not intended to
limit the scope of the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] The present disclosure will become more fully understood
from the detailed description and the accompanying drawings.
[0036] FIG. 1 is a block diagram of an example HVAC system
according to the prior art.
[0037] FIG. 2A is a functional block diagram of an example HVAC
system including an implementation of an air handler monitor
module.
[0038] FIG. 2B is a functional block diagram of an example HVAC
system including an implementation of a condensing monitor
module.
[0039] FIG. 2C is a functional block diagram of an example HVAC
system based on a heat pump.
[0040] FIG. 3 is a high level functional block diagram of an
example system including an implementation of a remote monitoring
system.
[0041] FIG. 4 is a table of example current values corresponding to
operating modes of a particular HVAC system installation.
[0042] FIGS. 5A-5B are functional block diagrams showing additional
detail of example control lines between a thermostat and a control
module.
[0043] FIG. 6 is a flowchart of example operation of a monitoring
system that determines operating mode of an HVAC system based on
control line current.
[0044] In the drawings, reference numbers may be reused to identify
similar and/or identical elements.
DETAILED DESCRIPTION
[0045] According to the present disclosure, a monitoring system can
be integrated with a residential or light commercial HVAC (heating,
ventilation, or air conditioning) system of a building. The
monitoring system can provide information on the status,
maintenance, and efficiency of the HVAC system to customers and/or
contractors associated with the building. For example, the building
may be a single-family residence, and the customer may be the
homeowner, a landlord, or a tenant. In other implementations, the
building may be a light commercial building, and the customer may
be the building owner, a tenant, or a property management
company.
[0046] As used in this application, the term HVAC can encompass all
environmental comfort systems in a building, including heating,
cooling, humidifying, dehumidifying, and air exchanging and
purifying, and covers devices such as furnaces, heat pumps,
humidifiers, dehumidifiers, and air conditioners. HVAC systems as
described in this application do not necessarily include both
heating and air conditioning, and may instead have only one or the
other.
[0047] In split HVAC systems with an air handler unit (often,
located indoors) and a condensing unit (often, located outdoors),
an air handler monitor module and a condensing monitor module,
respectively, can be used. The air handler monitor module and the
condensing monitor module may be integrated by the manufacturer of
the HVAC system, may be added at the time of the installation of
the HVAC system, and/or may be retrofitted to an existing HVAC
system.
[0048] In heat pump systems, the function of the air handler unit
and the condensing unit are reversed depending on the mode of the
heat pump. As a result, although the present disclosure uses the
terms air handler unit and condensing unit, the terms indoor unit
and outdoor unit could be used instead in the context of a heat
pump. The terms indoor unit and outdoor unit emphasize that the
physical locations of the components stay the same while their
roles change depending on the mode of the heat pump. A reversing
valve selectively reverses the flow of refrigerant from what is
shown in FIG. 1 depending on whether the system is heating the
building or cooling the building. When the flow of refrigerant is
reversed, the roles of the evaporator and condenser are
reversed--i.e., refrigerant evaporation occurs in what is labeled
the condenser while refrigerant condensation occurs in what is
labeled as the evaporator.
[0049] The air handler monitor and condensing monitor modules
monitor operating parameters of associated components of the HVAC
system. For example, the operating parameters may include power
supply current, power supply voltage, operating and ambient
temperatures of inside and outside air, refrigerant temperatures at
various points in the refrigerant loop, fault signals, control
signals, and humidity of inside and outside air.
[0050] The principles of the present disclosure may be applied to
monitoring other systems, such as a hot water heater, a boiler
heating system, a refrigerator, a refrigeration case, a pool
heater, a pool pump/filter, etc. As an example, the hot water
heater may include an igniter, a gas valve (which may be operated
by a solenoid), an igniter, an inducer blower, and a pump. The
monitoring system may analyze aggregate current readings to assess
operation of the individual components of the hot water heater.
[0051] The air handler monitor and condensing monitor modules may
communicate data between each other, while one or both of the air
handler monitor and condensing monitor modules upload data to a
remote location. The remote location may be accessible via any
suitable network, including the Internet.
[0052] The remote location includes one or more computers, which
will be referred to as servers. The servers execute a monitoring
system on behalf of a monitoring company. The monitoring system
receives and processes the data from the air handler monitor and
condensing monitor modules of customers who have such systems
installed. The monitoring system can provide performance
information, diagnostic alerts, and error messages to a customer
and/or third parties, such as designated HVAC contractors.
[0053] A server of the monitoring system includes a processor and
memory. The memory stores application code that processes data
received from the air handler monitor and condensing monitor
modules and determines existing and/or impending failures, as
described in more detail below. The processor executes this
application code and stores received data either in the memory or
in other forms of storage, including magnetic storage, optical
storage, flash memory storage, etc. While the term server is used
in this application, the application is not limited to a single
server.
[0054] A collection of servers may together operate to receive and
process data from the air handler monitor and condensing monitor
modules of multiple buildings. A load balancing algorithm may be
used between the servers to distribute processing and storage. The
present application is not limited to servers that are owned,
maintained, and housed by a monitoring company. Although the
present disclosure describes diagnostics and processing and
alerting occurring in a remote monitoring system, some or all of
these functions may be performed locally using installed equipment
and/or customer resources, such as on a customer computer or
computers.
[0055] Customers and/or HVAC contractors may be notified of current
and predicted issues affecting effectiveness or efficiency of the
HVAC system, and may receive notifications related to routine
maintenance. The methods of notification may take the form of push
or pull updates to an application, which may be executed on a smart
phone or other mobile device or on a standard computer.
Notifications may also be viewed using web applications or on local
displays, such as on a thermostat or other displays located
throughout the building or on a display (not shown) implemented in
the air handler monitor module or the condensing monitor module.
Notifications may also include text messages, emails, social
networking messages, voicemails, phone calls, etc.
[0056] The air handler monitor and condensing monitor modules may
each sense an aggregate current for the respective unit without
measuring individual currents of individual components. The
aggregate current data may be processed using frequency domain
analysis, statistical analysis, and state machine analysis to
determine operation of individual components based on the aggregate
current data. This processing may happen partially or entirely in a
server environment, remote from the customer's building or
residence.
[0057] The frequency domain analysis may allow individual
contributions of HVAC system components to be determined. Some of
the advantages of using an aggregate current measurement may
include reducing the number of current sensors that would otherwise
be necessary to monitor each of the HVAC system components. This
reduces bill of materials costs, as well as installation costs and
potential installation problems. Further, providing a single
time-domain current stream may reduce the amount of bandwidth
necessary to upload the current data. Nevertheless, the present
disclosure could also be used with additional current sensors.
[0058] Based on measurements from the air handler monitor and
condensing monitor modules, the monitoring company can determine
whether HVAC components are operating at their peak performance and
can advise the customer and the contractor when performance is
reduced. This performance reduction may be measured for the system
as a whole, such as in terms of efficiency, and/or may be monitored
for one or more individual components.
[0059] In addition, the monitoring system may detect and/or predict
failures of one or more components of the system. When a failure is
detected, the customer can be notified and potential remediation
steps can be taken immediately. For example, components of the HVAC
system may be shut down to prevent or minimize damage, such as
water damage, to HVAC components. The contractor can also be
notified that a service call will be required. Depending on the
contractual relationship between the customer and the contractor,
the contractor may immediately schedule a service call to the
building.
[0060] The monitoring system may provide specific information to
the contractor, including identifying information of the customer's
HVAC system, including make and model numbers, as well as
indications of the specific part numbers that appear to be failing.
Based on this information, the contractor can allocate the correct
repair personnel that have experience with the specific HVAC system
and/or component. In addition, the service technician is able to
bring replacement parts, avoiding return trips after diagnosis.
[0061] Depending on the severity of the failure, the customer
and/or contractor may be advised of relevant factors in determining
whether to repair the HVAC system or replace some or all of the
components of the HVAC system. For example only, these factors may
include relative costs of repair versus replacement, and may
include quantitative or qualitative information about advantages of
replacement equipment. For example, expected increases in
efficiency and/or comfort with new equipment may be provided. Based
on historical usage data and/or electricity or other commodity
prices, the comparison may also estimate annual savings resulting
from the efficiency improvement.
[0062] As mentioned above, the monitoring system may also predict
impending failures. This allows for preventative maintenance and
repair prior to an actual failure. Alerts regarding detected or
impending failures reduce the time when the HVAC system is out of
operation and allows for more flexible scheduling for both the
customer and contractor. If the customer is out of town, these
alerts may prevent damage from occurring when the customer is not
present to detect the failure of the HVAC system. For example,
failure of heat in winter may lead to pipes freezing and
bursting.
[0063] Alerts regarding potential or impending failures may specify
statistical timeframes before the failure is expected. For example
only, if a sensor is intermittently providing bad data, the
monitoring system may specify an expected amount of time before it
is likely that the sensor effectively stops working due to the
prevalence of bad data. Further, the monitoring system may explain,
in quantitative or qualitative terms, how the current operation
and/or the potential failure will affect operation of the HVAC
system. This enables the customer to prioritize and budget for
repairs.
[0064] For the monitoring service, the monitoring company may
charge a periodic rate, such as a monthly rate. This charge may be
billed directly to the customer and/or may be billed to the
contractor. The contractor may pass along these charges to the
customer and/or may make other arrangements, such as by requiring
an up-front payment upon installation and/or applying surcharges to
repairs and service visits.
[0065] For the air handler monitor and condensing monitor modules,
the monitoring company or contractor may charge the customer the
equipment cost, including the installation cost, at the time of
installation and/or may recoup these costs as part of the monthly
fee. Alternatively, rental fees may be charged for the air handler
monitor and condensing monitor modules, and once the monitoring
service is stopped, the air handler monitor and condensing monitor
modules may be returned.
[0066] The monitoring service may allow the customer and/or
contractor to remotely monitor and/or control HVAC components, such
as setting temperature, enabling or disabling heating and/or
cooling, etc. In addition, the customer may be able to track energy
usage, cycling times of the HVAC system, and/or historical data.
Efficiency and/or operating costs of the customer's HVAC system may
be compared against HVAC systems of neighbors, whose buildings will
be subject to the same or similar environmental conditions. This
allows for direct comparison of HVAC system and overall building
efficiency because environmental variables, such as temperature and
wind, are controlled.
[0067] The installer can provide information to the remote
monitoring system including identification of control lines that
were connected to the air handler monitor module and condensing
monitor module. In addition, information such as the HVAC system
type, year installed, manufacturer, model number, BTU rating,
filter type, filter size, tonnage, etc.
[0068] In addition, because the condensing unit may have been
installed separately from the furnace, the installer may also
record and provide to the remote monitoring system the manufacturer
and model number of the condensing unit, the year installed, the
refrigerant type, the tonnage, etc. Upon installation, baseline
tests are run. For example, this may include running a heating
cycle and a cooling cycle, which the remote monitoring system
records and uses to identify initial efficiency metrics. Further,
baseline profiles for current, power, and frequency domain current
can be established.
[0069] The server may store baseline data for the HVAC system of
each building. The baselines can be used to detect changes
indicating impending or existing failures. For example only,
frequency-domain current signatures of failures of various
components may be pre-programmed, and may be updated based on
observed evidence from contractors. For example, once a malfunction
in an HVAC system is recognized, the monitoring system may note the
frequency data leading up to the malfunction and correlate that
frequency signature with frequency signatures associated with
potential causes of the malfunction. For example only, a computer
learning system, such as a neural network or a genetic algorithm,
may be used to refine frequency signatures. The frequency
signatures may be unique to different types of HVAC systems but may
share common characteristics. These common characteristics may be
adapted based on the specific type of HVAC system being
monitored.
[0070] The installer may collect a device fee, an installation fee,
and/or a subscription fee from the customer. In various
implementations, the subscription fee, the installation fee, and
the device fee may be rolled into a single system fee, which the
customer pays upon installation. The system fee may include the
subscription fee for a set number of years, such as 1, 2, 5, or 10,
or may be a lifetime subscription, which may last for the life of
the home or the ownership of the building by the customer.
[0071] The monitoring system can be used by the contractor during
and after installation and during and after repair (i) to verify
operation of the air handler monitor and condensing monitor
modules, as well as (ii) to verify correct installation of the
components of the HVAC system. In addition, the customer may review
this data in the monitoring system for assurance that the
contractor correctly installed and configured the HVAC system. In
addition to being uploaded to the remote monitoring service (also
referred to as the cloud), monitored data may be transmitted to a
local device in the building. For example, a smartphone, laptop, or
proprietary portable device may receive monitoring information to
diagnose problems and receive real-time performance data.
Alternatively, data may be uploaded to the cloud and then
downloaded onto a local computing device, such as via the Internet
from an interactive web site.
[0072] The historical data collected by the monitoring system may
allow the contractor to properly specify new HVAC components and to
better tune configuration, including dampers and set points of the
HVAC system. The information collected may be helpful in product
development and assessing failure modes. The information may be
relevant to warranty concerns, such as determining whether a
particular problem is covered by a warranty. Further, the
information may help to identify conditions, such as unauthorized
system modifications, that could potentially void warranty
coverage.
[0073] Original equipment manufacturers may subsidize partially or
fully the cost of the monitoring system and air handler and
condensing monitor modules in return for access to this
information. Installation and service contractors may also
subsidize some or all of these costs in return for access to this
information, and for example, in exchange for being recommended by
the monitoring system. Based on historical service data and
customer feedback, the monitoring system may provide contractor
recommendations to customers.
[0074] FIGS. 2A-2B are functional block diagrams of an example
monitoring system associated with an HVAC system of a building. The
air handler unit 136 of FIG. 1 is shown for reference. Because the
monitoring systems of the present disclosure can be used in
retrofit applications, elements of the air handler unit 136 may
remain unmodified. An air handler monitor module 200 and a
condensing monitor module 204 can be installed in an existing
system without needing to replace the original thermostat 116 shown
in FIG. 1. To enable certain additional functionality, however,
such as WiFi thermostat control and/or thermostat display of alert
messages, the thermostat 116 of FIG. 1 may be replaced with a
thermostat 208 having networking capability.
[0075] In many systems, the air handler unit 136 is located inside
the building, while the condensing unit 164 is located outside the
building. The present disclosure is not limited, and applies to
other systems including, as examples only, systems where the
components of the air handler unit 136 and the condensing unit 164
are located in close proximity to each other or even in a single
enclosure. The single enclosure may be located inside or outside of
the building. In various implementations, the air handler unit 136
may be located in a basement, garage, or attic. In ground source
systems, where heat is exchanged with the earth, the air handler
unit 136 and the condensing unit 164 may be located near the earth,
such as in a basement, crawlspace, garage, or on the first floor,
such as when the first floor is separated from the earth by only a
concrete slab.
[0076] In FIG. 2A, the air handler monitor module 200 is shown
external to the air handler unit 136, although the air handler
monitor module 200 may be physically located outside of, in contact
with, or even inside of an enclosure, such as a sheet metal casing,
of the air handler unit 136.
[0077] When installing the air handler monitor module 200 in the
air handler unit 136, power is provided to the air handler monitor
module 200. For example, a transformer 212 can be connected to an
AC line in order to provide AC power to the air handler monitor
module 200. The air handler monitor module 200 may measure voltage
of the incoming AC line based on this transformed power supply. For
example, the transformer 212 may be a 10-to-1 transformer and
therefore provide either a 12V or 24V AC supply to the air handler
monitor module 200 depending on whether the air handler unit 136 is
operating on nominal 120 volt or nominal 240 volt power. The air
handler monitor module 200 then receives power from the transformer
212 and determines the AC line voltage based on the power received
from the transformer 212.
[0078] For example, frequency, amplitude, RMS voltage, and DC
offset may be calculated based on the measured voltages. In
situations where 3-phase power is used, the order of the phases may
be determined. Information about when the voltage crosses zero may
be used to synchronize various measurements and to determine
frequency of the AC power based on counting the number of zero
crossings within a predetermine time period.
[0079] A current sensor 216 measures incoming current to the air
handler unit 136. The current sensor 216 may include a current
transformer that snaps around one power lead of the incoming AC
power. The current sensor 216 may alternatively include a current
shunt or a hall effect device. In various implementations, a power
sensor (not shown) may be used in addition to or in place of the
current sensor 216.
[0080] In various other implementations, electrical parameters
(such as voltage, current, and power factor) may be measured at a
different location, such as at an electrical panel providing power
to the building from the electrical utility.
[0081] For simplicity of illustration, the control module 112 is
not shown to be connected to the various components and sensors of
the air handler unit 136. In addition, routing of the AC power to
various powered components of the air handler unit 136, such as the
circulator blower 108, the gas valve 128, and the inducer blower
132, are also not shown for simplicity. The current sensor 216
measures the current entering the air handler unit 136 and
therefore represents an aggregate current of the current-consuming
components of the air handler unit 136.
[0082] The control module 112 controls operation in response to
signals from a thermostat 208 received over control lines. The air
handler monitor module 200 monitors the control lines. The control
lines may include a call for cool, a call for heat, and a call for
fan. The control lines may include a line corresponding to a state
of a reversing valve in heat pump systems.
[0083] The control lines may further carry calls for secondary heat
and/or secondary cooling, which may be activated when the primary
heating or primary cooling is insufficient. In dual fuel systems,
such as systems operating from either electricity or natural gas,
control signals related to the selection of the fuel may be
monitored. Further, additional status and error signals may be
monitored, such as a defrost status signal, which may be asserted
when the compressor is shut off and a defrost heater operates to
melt frost from an evaporator.
[0084] The control lines may be monitored by attaching leads to
terminal blocks at the control module 112 at which the fan and heat
signals are received. These terminal blocks may include additional
connections where leads can be attached between these additional
connections and the air handler monitor module 200. Alternatively,
leads from the air handler monitor module 200 may be attached to
the same location as the fan and heat signals, such as by putting
multiple spade lugs underneath a signal screw head.
[0085] In various implementations, the cool signal from the
thermostat 208 may be disconnected from the control module 112 and
attached to the air handler monitor module 200. The air handler
monitor module 200 can then provide a switched cool signal to the
control module 112. This allows the air handler monitor module 200
to interrupt operation of the air conditioning system, such as upon
detection of water by one of the water sensors. The air handler
monitor module 200 may also interrupt operation of the air
conditioning system based on information from the condensing
monitor module 204, such as detection of a locked rotor condition
in the compressor.
[0086] A condensate sensor 220 measures condensate levels in the
condensate pan 146. If a level of condensate gets too high, this
may indicate a plug or clog in the condensate pan 146 or a problem
with hoses or pumps used for drainage from the condensate pan 146.
The condensate sensor 220 may be installed along with the air
handler monitor module 200 or may already be present. When the
condensate sensor 220 is already present, an electrical interface
adapter may be used to allow the air handler monitor module 200 to
receive the readings from the condensate sensor 220. Although shown
in FIG. 2A as being internal to the air handler unit 136, access to
the condensate pan 146, and therefore the location of the
condensate sensor 220, may be external to the air handler unit
136.
[0087] Additional water sensors, such as a conduction (wet floor)
sensor may also be installed. The air handler unit 136 may be
located on a catch pan, especially in situations where the air
handler unit 136 is located above living space of the building. The
catch pan may include a float switch. When enough liquid
accumulates in the catch pan, the float switch provides an
over-level signal, which may be sensed by the air handler monitor
module 200.
[0088] A return air sensor 224 is located in a return air plenum
228. The return air sensor 224 may measure temperature and may also
measure mass airflow. In various implementations, a thermistor may
be multiplexed as both a temperature sensor and a hot wire mass
airflow sensor. In various implementations, the return air sensor
224 is upstream of the filter 104 but downstream of any bends in
the return air plenum 228.
[0089] A supply air sensor 232 is located in a supply air plenum
236. The supply air sensor 232 may measure air temperature and may
also measure mass airflow. The supply air sensor 232 may include a
thermistor that is multiplexed to measure both temperature and, as
a hot wire sensor, mass airflow. In various implementations, such
as is shown in FIG. 2A, the supply air sensor 232 may be located
downstream of the evaporator 144 but upstream of any bends in the
supply air plenum 236.
[0090] A differential pressure reading may be obtained by placing
opposite sensing inputs of a differential pressure sensor (not
shown) in the return air plenum 228 and the supply air plenum 236,
respectively. For example only, these sensing inputs may be
collocated or integrated with the return air sensor 224 and the
supply air sensor 232, respectively. In various implementations,
discrete pressure sensors may be placed in the return air plenum
228 and the supply air plenum 236. A differential pressure value
can then be calculated by subtracting the individual pressure
values.
[0091] The air handler monitor module 200 also receives a suction
line temperature from a suction line temperature sensor 240. The
suction line temperature sensor 240 measures refrigerant
temperature in the refrigerant line between the evaporator 144 of
FIG. 2A and the compressor 148 of FIG. 2B. A liquid line
temperature sensor 244 measures the temperature of refrigerant in a
liquid line traveling from the condenser 152 of FIG. 2B to the
expansion valve 140 of FIG. 2A.
[0092] The air handler monitor module 200 may include one or more
expansion ports to allow for connection of additional sensors
and/or to allow connection to other devices, such as a home
security system, a proprietary handheld device for use by
contractors, or a portable computer.
[0093] The air handler monitor module 200 also monitors control
signals from the thermostat 208. Because one or more of these
control signals is also transmitted to the condensing unit 164 of
FIG. 2B, these control signals can be used for communication
between the air handler monitor module 200 and the condensing
monitor module 204 of FIG. 2B.
[0094] The air handler monitor module 200 may transmit frames of
data corresponding to periods of time. For example only, 7.5 frames
may span one second (i.e., 0.1333 seconds per frame). Each frame of
data may include voltage, current, temperatures, control line
status, and water sensor status. Calculations may be performed for
each frame of data, including averages, powers, RMS, and FFT. Then
the frame is transmitted to the monitoring system.
[0095] The voltage and current signals may be sampled by an
analog-to-digital converter at a certain rate, such as 1920 samples
per second. The frame length may be measured in terms of samples.
When a frame is 256 samples long, at a sample rate of 1920 samples
per second, there will be 7.5 frames per second.
[0096] The sampling rate of 1920 Hz has a Nyquist frequency of 960
Hz and therefore allows an FFT bandwidth of up to approximately 960
Hz. An FFT limited to the time span of a single frame may be
calculated for each frame. Then, for that frame, instead of
transmitting all of the raw current data, only statistical data
(such as average current) and frequency-domain data are
transmitted.
[0097] This gives the monitoring system current data having a 7.5
Hz resolution, and gives frequency-domain data with approximately
the 960 Hz bandwidth. The time-domain current and/or the derivative
of the time-domain current may be analyzed to detect impending or
existing failures. In addition, the current and/or the derivative
may be used to determine which set of frequency-domain data to
analyze. For example, certain time-domain data may indicate the
approximate window of activation of a hot surface igniter, while
frequency-domain data is used to assess the state of repair of the
hot surface igniter.
[0098] In various implementations, the air handler monitor module
200 may only transmit frames during certain periods of time. These
periods may be critical to operation of the HVAC system. For
example, when thermostat control lines change, the air handler
monitor module 200 may record data and transmit frames for a
predetermined period of time after that transition. Then, if the
HVAC system is operating, the air handler monitor module 200 may
intermittently record data and transmit frames until operation of
the HVAC system has completed.
[0099] The air handler monitor module 200 transmits data measured
by both the air handler monitor module 200 itself and the
condensing monitor module 204 over a wide area network 248, such as
the Internet (referred to as the Internet 248). The air handler
monitor module 200 may access the Internet 248 using a router 252
of the customer. The customer router 252 may already be present to
provide Internet access to other devices (not shown) within the
building, such as a customer computer and/or various other devices
having Internet connectivity, such as a DVR (digital video
recorder) or a video gaming system.
[0100] The air handler monitor module 200 communicates with the
customer router 252 using a proprietary or standardized, wired or
wireless protocol, such as Bluetooth, ZigBee (IEEE 802.15.4), 900
Megahertz, 2.4 Gigahertz, WiFi (IEEE 802.11). In various
implementations, a gateway 256 is implemented, which creates a
wireless network with the air handler monitor module 200. The
gateway 256 may interface with the customer router 252 using a
wired or wireless protocol, such as Ethernet (IEEE 802.3).
[0101] The thermostat 208 may also communicate with the customer
router 252 using WiFi. Alternatively, the thermostat 208 may
communicate with the customer router 252 via the gateway 256. In
various implementations, the air handler monitor module 200 and the
thermostat 208 do not communicate directly. However, because they
are both connected through the customer router 252 to a remote
monitoring system, the remote monitoring system may allow for
control of one based on inputs from the other. For example, various
faults identified based on information from the air handler monitor
module 200 may cause the remote monitoring system to adjust
temperature set points of the thermostat 208 and/or display warning
or alert messages on the thermostat 208.
[0102] In various implementations, the transformer 212 may be
omitted, and the air handler monitor module 200 may include a power
supply that is directly powered by the incoming AC power. Further,
power-line communications may be conducted over the AC power line
instead of over a lower-voltage HVAC control line.
[0103] In various implementations, the current sensor 400 may be
omitted, and instead a voltage sensor (not shown) may be used. The
voltage sensor measures the voltage of an output of a transformer
internal to the control module 112, the internal transformer
providing the power (e.g., 24 Volts) for the control signals. The
air handler monitor module 200 may measure the voltage of the
incoming AC power and calculate a ratio of the voltage input to the
internal transformer to the voltage output from the internal
transformer. As the current load on the internal transformer
increases, the impedance of the internal transformer causes the
voltage of the output power to decrease. Therefore, the current
draw from the internal transformer can be inferred from the
measured ratio (also called an apparent transformer ratio). The
inferred current draw may be used in place of the measured
aggregate current draw described in the present disclosure.
[0104] In FIG. 2B, the condensing monitor module 204 is installed
in the condensing unit 164. A transformer 260 converts incoming AC
voltage into a stepped-down voltage for powering the condensing
monitor module 204. In various implementations, the transformer 260
may be a 10-to-1 transformer. A current sensor 264 measures current
entering the condensing unit 164. The condensing monitor module 204
may also measure voltage from the supply provided by the
transformer 260. Based on measurements of the voltage and current,
the condensing monitor module 204 may calculate power and/or may
determine power factor.
[0105] A liquid line temperature sensor 266 measures the
temperature of refrigerant traveling from the condenser 152 to the
air handler unit 136. In various implementations, the liquid line
temperature sensor 266 is located prior to any filter-drier, such
as the filter-drier 154 of FIG. 2A. In normal operation, the liquid
line temperature sensor 266 and the liquid line temperature sensor
246 of FIG. 2A may provide similar data, and therefore one of the
liquid line temperature sensors 246 or 266 may be omitted. However,
having both of the liquid line temperature sensors 246 and 266 may
allow for certain problems to be diagnosed, such as a kink or other
restriction in the refrigerant line between the air handler unit
136 and the condensing unit 164.
[0106] In various implementations, the condensing monitor module
204 may receive ambient temperature data from a temperature sensor
(not shown). When the condensing monitor module 204 is located
outdoors, the ambient temperature represents an outside ambient
temperature. The temperature sensor supplying the ambient
temperature may be located outside of an enclosure of the
condensing unit 164. Alternatively, the temperature sensor may be
located within the enclosure, but exposed to circulating air. In
various implementations the temperature sensor may be shielded from
direct sunlight and may be exposed to an air cavity that is not
directly heated by sunlight. Alternatively or additionally, online
(including Internet-based) weather data based on geographical
location of the building may be used to determine sun load, outside
ambient air temperature, precipitation, and humidity.
[0107] In various implementations, the condensing monitor module
204 may receive refrigerant temperature data from refrigerant
temperature sensors (not shown) located at various points, such as
before the compressor 148 (referred to as a suction line
temperature), after the compressor 148 (referred to as a compressor
discharge temperature), after the condenser 152 (referred to as a
liquid line out temperature), and/or at one or more points along a
coil of the condenser 152. The location of temperature sensors may
be dictated by a physical arrangement of the condenser coils.
Additionally or alternatively to the liquid line out temperature
sensor, a liquid line in temperature sensor may be used. An
approach temperature may be calculated, which is a measure of how
close the condenser 152 has been able to bring the liquid line out
temperature to the ambient air temperature.
[0108] During installation, the location of the temperature sensors
may be recorded. Additionally or alternatively, a database may be
maintained that specifies where temperature sensors are placed.
This database may be referenced by installers and may allow for
accurate remote processing of the temperature data. The database
may be used for both air handler sensors and compressor/condenser
sensors. The database may be prepopulated by the monitoring company
or may be developed by trusted installers, and then shared with
other installation contractors.
[0109] As described above, the condensing monitor module 204 may
communicate with the air handler monitor module 200 over one or
more control lines from the thermostat 208. In these
implementations, data from the condensing monitor module 204 is
transmitted to the air handler monitor module 200, which in turn
uploads the data over the Internet 248.
[0110] In various implementations, the transformer 260 may be
omitted, and the condensing monitor module 204 may include a power
supply that is directly powered by the incoming AC power. Further,
power-line communications may be conducted over the AC power line
instead of over a lower-voltage HVAC control line.
[0111] In FIG. 2C, an example condensing unit 268 is shown for a
heat pump implementation. The condensing unit 268 may be configured
similarly to the condensing unit 164 of FIG. 2B. Similarly to FIG.
2B, the transformer 260 may be omitted in various implementations.
Although referred to as the condensing unit 268, the mode of the
heat pump determines whether the condenser 152 of the condensing
unit 268 is actually operating as a condenser or as an evaporator.
A reversing valve 272 is controlled by a control module 276 and
determines whether the compressor 148 discharges compressed
refrigerant toward the condenser 152 (cooling mode) or away from
the condenser 152 (heating mode).
[0112] In various implementations, a current sensor 280 is
implemented to measure one or more currents of the control signals.
The current sensor 280 may measure an aggregate current of all the
control lines arriving at the condensing unit 268. The aggregate
current may be obtained by measuring the current of a common
control return conductor. The aggregate current measured by the
current sensor 280 may be used to determine the state of multiple
heat pump control signals, such as signals that control operation
of defrosting functions and the reversing valve. The aggregate
current measured by the current sensor 280 may also be used to
determine the state of calls for varying levels of compressor
capacity. While not shown, the current sensor 280 may similarly be
installed in the condensing unit 164.
[0113] In FIG. 3, the air handler monitor module 200 and the
thermostat 208 are shown communicating, using the customer router
252, with a remote monitoring system 304 via the Internet 248. In
other implementations, the condensing monitor module 204 may
transmit data from the air handler monitor module 200 and the
condensing monitor module 204 to an external wireless receiver. The
external wireless receiver may be a proprietary receiver for a
neighborhood in which the building is located, or may be an
infrastructure receiver, such as a metropolitan area network (such
as WiMAX), a WiFi access point, or a mobile phone base station.
[0114] The remote monitoring system 304 includes a monitoring
server 308 that receives data from the air handler monitor module
200 and the thermostat 208 and maintains and verifies network
continuity with the air handler monitor module 200. The monitoring
server 308 executes various algorithms to identify problems, such
as failures or decreased efficiency, and to predict impending
faults.
[0115] The monitoring server 308 may notify a review server 312
when a problem is identified or a fault is predicted. This
programmatic assessment may be referred to as an advisory. Some or
all advisories may be triaged by a technician to reduce false
positives and potentially supplement or modify data corresponding
to the advisory. For example, a technician device 316 operated by a
technician is used to review the advisory and to monitor data (in
various implementations, in real-time) from the air handler monitor
module 200 via the monitoring server 308.
[0116] The technician using the technician device 316 reviews the
advisory. If the technician determines that the problem or fault is
either already present or impending, the technician instructs the
review server 312 to send an alert to either or both of a
contractor device 320 or a customer device 324. The technician may
determine that, although a problem or fault is present, the cause
is more likely to be something different than specified by the
automated advisory. The technician can therefore issue a different
alert or modify the advisory before issuing an alert based on the
advisory. The technician may also annotate the alert sent to the
contractor device 320 and/or the customer device 324 with
additional information that may be helpful in identifying the
urgency of addressing the alert and presenting data that may be
useful for diagnosis or troubleshooting.
[0117] In various implementations, minor problems may be reported
to the contractor device 320 only so as not to alarm the customer
or inundate the customer with alerts. Whether the problem is
considered to be minor may be based on a threshold. For example, an
efficiency decrease greater than a predetermined threshold may be
reported to both the contractor and the customer, while an
efficiency decrease less than the predetermined threshold is
reported to only the contractor.
[0118] In some circumstances, the technician may determine that an
alert is not warranted based on the advisory. The advisory may be
stored for future use, for reporting purposes, and/or for adaptive
learning of advisory algorithms and thresholds. In various
implementations, a majority of generated advisories may be closed
by the technician without sending an alert.
[0119] Based on data collected from advisories and alerts, certain
alerts may be automated. For example, analyzing data over time may
indicate that whether a certain alert is sent by a technician in
response to a certain advisory depends on whether a data value is
on one side of a threshold or another. A heuristic can then be
developed that allows those advisories to be handled automatically
without technician review. Based on other data, it may be
determined that certain automatic alerts had a false positive rate
over a threshold. These alerts may be put back under the control of
a technician.
[0120] In various implementations, the technician device 316 may be
remote from the remote monitoring system 304 but connected via a
wide area network. For example only, the technician device 316 may
include a computing device such as a laptop, desktop, or
tablet.
[0121] With the contractor device 320, the contractor can access a
contractor portal 328, which provides historical and real-time data
from the air handler monitor module 200. The contractor using the
contractor device 320 may also contact the technician using the
technician device 316. The customer using the customer device 324
may access a customer portal 332 in which a graphical view of the
system status as well as alert information is shown. The contractor
portal 328 and the customer portal 332 may be implemented in a
variety of ways according to the present disclosure, including as
an interactive web page, a computer application, and/or an app for
a smartphone or tablet.
[0122] In various implementations, data shown by the customer
portal may be more limited and/or more delayed when compared to
data visible in the contractor portal 328. In various
implementations, the contractor device 320 can be used to request
data from the air handler monitor module 200, such as when
commissioning a new installation.
[0123] In various implementations, some of all of the functionality
of the remote monitoring system 304 may be local instead of remote
from the building. For example only, some or all of the
functionality may be integrated with the air handler monitor module
200 or the condensing monitor module 204. Alternatively, a local
controller may implement some of all of the functionality of the
remote monitoring system 304.
[0124] Detection of various faults may require knowledge of which
mode the HVAC system is operating in, and more specifically, which
mode has been commanded by the thermostat. A heating fault may be
identified when, for a given call for heat pattern, the
supply/return air temperature split indicates insufficient heating.
The threshold may be set at a predetermined percentage of the
expected supply/return air temperature split.
[0125] A heating shutdown fault may be determined when a
temperature split rises to within an expected range but then falls
below the expected range. This may indicate that one or more of the
pressure sensors has caused the heating to stop. As these shutdowns
become more frequent, a more severe fault may be declared,
indicating that the heater may soon fail to provide adequate heat
for the conditioned space because the heater is repeatedly shutting
down.
[0126] When a call for heat is made, the furnace will progress
through a sequence of states. For example only, the sequence may
begin with activating the inducer blower, opening the gas valve,
igniting the gas, and turning on the circulator blower. Each of
these states may be detectable in current data, although
frequency-domain as well as time-domain data may be necessary to
reliably determine certain states. When this sequence of states
appears to indicate that the furnace is restarting, a fault may be
declared. A furnace restart may be detected when the measured
current matches a baseline current profile for a certain number of
states and then diverges from the baseline current profile for the
next state or states.
[0127] Furnace restarts may occur occasionally for various reasons,
but as the number and frequency of furnace restart events
increases, an eventual fault is predicted. For example only, if 50%
of calls for heat involve one or more furnace restarts, a fault may
be declared indicating that soon the furnace may fail to start
altogether or may require so many restarts that sufficient heating
will not be available.
[0128] An overheating fault may be declared when a temperature
exceeds an expected value, such a baseline value, by more than a
predetermined amount. For example, when the supply/return air
temperature split is greater than a predetermined threshold, the
heat exchanger may be operating at too high of a temperature.
[0129] A flame rollout switch is a safety device that detects
overly high burner assembly temperatures, which may be caused by a
reduction in airflow, such as a restricted flue. A fault in the
flame rollout switch may be diagnosed based on states of the
furnace sequence, as determined by measured current. For example, a
trip of the flame rollout switch may generally occur during the
same heating state for a given system. In various implementations,
the flame rollout switch will be a single-use protection mechanism,
and therefore a trip of the flame rollout switch is reported as a
fault that will prevent further heating from occurring.
[0130] A blower fault is determined based on variation of measured
current from a baseline. The measured current may be normalized
according to measured voltage, and differential pressure may also
be used to identify a blower fault. As the duration and magnitude
of deviation between the measured current and the expected current
increase, the severity of the fault increases. As the current drawn
by the blower goes up, the risk of a circuit breaker or internal
protection mechanism tripping increases, which may lead to loss of
heating.
[0131] A permanent-split capacitor motor is a type of AC induction
motor. A fault in this motor may be detected based on variation of
power, power factor, and variation from a baseline. A fault in this
motor, which may be used as a circulator blower, may be confirmed
based on a differential air pressure. As the deviation increases,
the severity of the fault increases.
[0132] A fault with spark ignition may be detected based on fault
of the furnace to progress passed the state at which the spark
ignition should ignite the air/fuel mixture. A signature of the
spark igniter may be baselined in the frequency domain. Absence of
this profile at the expected time may indicate that the spark
igniter has failed to operate. Meanwhile, when a profile
corresponding to the spark igniter is present but deviates from the
baseline, this is an indication that the spark igniter may be
failing. As the variation from the baseline increases, the risk of
fault increases. In addition to current-based furnace state
monitoring, the supply/return temperature split may verify that the
heater has failed to commence heating.
[0133] A hot surface igniter fault is detected based on analyzing
current to determine furnace states. When the current profile
indicates that igniter retries have occurred, this may indicate an
impending fault of the hot surface igniter. In addition, changes in
the igniter profile compared to a baseline may indicate an
impending fault. For example, an increase in drive level indicated
in either time-domain or frequency-domain current data, an increase
in effective resistance, or frequency domain indication of internal
arcing may indicate an impending fault of the hot surface
igniter.
[0134] A fault in the inducer fan or blower is detected based on
heater states determined according to current. Faults may be
predicted based on frequency domain analysis of inducer fan
operation that indicate operational problems, such as fan blades
striking the fan housing, water being present in the housing,
bearing issues, etc. In various implementations, analysis of the
inducer fan may be performed during a time window prior to the
circulator blower beginning. The current drawn by the circulator
blower may mask any current drawn by the inducer blower.
[0135] A fault in the fan pressure switch may be detected when the
time-domain current indicates that the furnace restarted but blower
fault does not appear to be present and ignition retries were not
performed. In other words, the furnace may be operating as expected
with the issue that the fan pressure switch does not recognize that
the blower motor is not operating correctly. Service may be called
to replace the fan pressure switch. In various implementations, the
fan pressure switch may fail gradually, and therefore an increase
in the number of furnace restarts attributed to the fan pressure
switch may indicate an impending fault with the fan pressure
switch.
[0136] A flame probe fault is detected when a flame has been
properly created, but the flame probe does not detect the flame.
This is determined when there are ignition retries but
frequency-domain data indicates that the igniter appears to be
operating properly. Frequency-domain data may also indicate that
the gas valve is functioning properly, isolating the fault to the
flame probe. A fault in the gas valve may be detected based on the
sequence of states in the furnace as indicated by the current.
Although the amount of current drawn by the gas valve may be small,
a signature corresponding to the gas valve may still be present in
the frequency domain. When the signature is not present, and the
furnace does not run, the absence of the signature may indicate a
fault with the gas valve.
[0137] A coil, such as an evaporator coil, may freeze, such as when
inadequate airflow fails to deliver enough heat to refrigerant in
the coil. Detecting a freezing coil may rely on a combination of
inputs, and depends on directional shifts in sensors including
temperatures, voltage, time domain current, frequency domain
current, power factor, and power measurements. In addition,
voltage, current, frequency domain current, and power data may
allow other faults to be ruled out.
[0138] A dirty filter may be detected in light of changes in power,
current, and power factor coupled with a decrease in temperature
split and reduced pressure. The power, current, and power factor
may be dependent on motor type. When a mass airflow sensor is
available, the mass flow sensor may be able to directly indicate a
flow restriction in systems using a permanent split capacitor
motor.
[0139] Faults with compressor capacitors, including run and start
capacitors, may be determined based on variations in power factor
of the condenser monitor module. A rapid change in power factor may
indicate an inoperative capacitor while a gradual change indicates
a degrading capacitor. Because capacitance varies with air
pressure, outside air temperature may be used to normalize power
factor and current data. A fault related to the circulator blower
or inducer blower resulting from an imbalanced bearing or a blade
striking the respective housing may be determined based on a
variation in frequency domain current signature.
[0140] A general failure to cool may be assessed after 15 minutes
from the call for cool. A difference between a supply air
temperature and return air temperature indicates that little or no
cooling is taking place on the supply air. A similar failure to
cool determination may be made after 30 minutes. If the system is
unable to cool by 15 minutes but is able to cool by 30 minutes,
this may be an indication that operation of the cooling system is
degrading and a fault may occur soon.
[0141] Low refrigerant charge may be determined when, after a call
for cool, supply and return temperature measurements exhibit lack
of cooling and a temperature differential between refrigerant in
the suction line and outside temperature varies from a baseline by
more than a threshold. In addition, low charge may be indicated by
decreasing power consumed by the condenser unit. An overcharge
condition of the refrigerant can be determined when, after a call
for cool, a difference between liquid line temperature and outside
air temperature is smaller than expected. A difference between
refrigerant temperature in the liquid line and outside temperature
is low compared to a baseline when refrigerant is overcharged.
[0142] Low indoor airflow may be assessed when a call for cool and
fan is present, and the differential between return and supply air
increases above a baseline, suction line decreases below a
baseline, pressure increases, and indoor current deviates from a
baseline established according to the motor type. Low outdoor
airflow through the condenser is determined when a call for cool is
present, and a differential between refrigerant temperature in the
liquid line and outside ambient temperature increases above a
baseline and outdoor current also increases above a baseline.
[0143] A possible flow restriction is detected when the
return/supply air temperature split and the liquid line temperature
is low while a call for cool is present. An outdoor run capacitor
fault may be declared when, while a call for cool is present, power
factor decreases rapidly. A general increase in power fault may be
declared when a call for cool is present and power increases above
a baseline. The baseline may be normalized according to outside air
temperature and may be established during initial runs of the
system, and/or may be specified by a manufacturer. A general fault
corresponding to a decrease in capacity may be declared when a call
for cool is present and the return/supply air temperature split,
air pressure, and indoor current indicate a decrease in
capacity.
[0144] In a heat pump system, a general failure to heat fault may
be declared after 15 minutes from when a call for heat occurred and
the supply/return air temperature split is below a threshold.
Similarly, a more severe fault is declared if the supply/return air
temperature split is below the same or different threshold after 30
minutes. A low charge condition of the heat pump may be determined
when a call for heat is present and a supply/return air temperature
split indicates a lack of heating, a difference between supply air
and liquid line temperatures is less than a baseline, and a
difference between return air temperature and liquid line
temperature is less than a baseline. A high charge condition of the
heat pump may be determined when a call for heat is present, a
difference between supply air temperature and liquid line
temperature is high, a difference between a liquid line temperature
and return air temperature is low, and outdoor power increases.
[0145] Low indoor airflow in a heat pump system, while a call for
heat and fan are present, is detected when the supply/return air
temperature split is high, pressure increases, and indoor current
deviates from a baseline, where the baseline is based on motor
type. Low outdoor airflow on a heat pump is detected when a call
for heat is present, the supply/return air temperature split
indicates a lack of heating as a function of outside air
temperature, and outdoor power increases.
[0146] A flow restriction in a heat pump system is determined when
a call for heat is present, supply/return air temperature split
does not indicate heating is occurring, runtime is increasing, and
a difference between supply air and liquid line temperature
increases. A general increase in power consumption fault for heat
pump system may indicate a loss of efficiency, and is detected when
a call for heat is present and power increases above a baseline as
a function of outside air temperature.
[0147] A capacity decrease in a heat pump system may be determined
when a call for heat is present, a supply/return air temperature
split indicates a lack of heating, and pressure split in indoor
current indicate a decreased capacity. Outside air temperature
affects capacity, and therefore the threshold to declare a low
capacity fault is adjusted in response to outside air
temperature.
[0148] A reversing valve fault is determined when a call for heat
is present but supply/return air temperature split indicates that
cooling is occurring. Similarly, a reversing valve fault is
determined when a call for cool is present but supply/return air
temperature split indicates that heating is occurring.
[0149] A defrost fault may be declared in response to outdoor
current, voltage, power, and power factor data, and supply/return
air temperature split, refrigerant supply line temperature, suction
line temperature, and outside air temperature indicating that frost
is occurring on the outdoor coil, and defrost has failed to
activate. When a fault due to the reversing valve is ruled out, a
general defrost fault may be declared.
[0150] Excessive compressor tripping in a heat pump system may be
determined when a call for cool or heating is present,
supply/return air temperature split lacks indication of the
requested cooling or heating, and outdoor fan motor current rapidly
decreases. A fault for compressor short cycling due to pressure
limits being exceeded may be detected when a call for cool is
present, supply/return air temperature split does not indicate
cooling, and there is a rapid decrease in outdoor current and a
short runtime. A compressor bearing fault may be declared when an
FFT of outdoor current indicates changes in motor loading, support
for this fault is provided by power factor measurement. A locked
rotor of the compressor motor may be determined when excessive
current is present at a time when the compressor is slow to start.
A locked rotor is confirmed with power and power factor
measurements.
[0151] Thermostat short cycling is identified when a call for cool
is removed prior to a full cooling sequence being completed. For
example, this may occur when a supply register is too close to the
thermostat, and leads to the thermostat prematurely believing the
house has reached a desired temperature.
[0152] When a call for heat and a call for cool are present at the
same time, a fault with the thermostat or with the control signal
wiring is present. When independent communication between a monitor
module and a thermostat is possible, such as when a thermostat is
Internet-enabled, thermostat commands can be compared to actual
signals on control lines and discrepancies indicate faults in
control signal wiring.
[0153] Returning back to FIG. 2A, in order for the monitoring
system to determine which mode the HVAC system is operating in,
each control signal between the thermostat 208 and the control
module 112 may be monitored. Because the monitoring system of the
present disclosure can be used in a retrofit environment, this may
require connecting leads to each of the control lines. Making
individual connections requires additional installation time and
therefore expense. As the number of connections increase, the
number of opportunities for a loose connection, and therefore
erroneous readings, increase.
[0154] Further, because connecting leads may require removing and
reattaching control lines from the control module, the loose
connection may even affect normal operation of the HVAC system,
such as the ability of the thermostat 208 to control certain
aspects of the control module 112. Further, a location at which the
control lines are accessible may be difficult for an installer to
reach without removing other components of the HVAC system, which
increases installation time and also increases the risk of
introducing problems.
[0155] With multiple connections, even when the control lines are
successfully connected, there is a risk that the connections will
be misidentified--e.g., leading the monitoring system to believe
that a call for cool has been made by the thermostat 208 when, in
fact, a call for heat was instead made. Some HVAC systems may use
those control lines in a non-standard way. Again, this may lead to
misinterpretation of the control signals by the monitoring system.
A further complication is introduced by "communicating systems,"
which do not rely on standard HVAC control lines and instead
multiplex multiple signals onto one or more control lines. For
example only, in a communicating system the thermostat 208 and the
control module 112 may perform bidirectional digital communication
using two or more lines. As a result, individual control lines
corresponding to each mode of operation of the HVAC system may not
be present.
[0156] The present disclosure presents an alternative to
individually sensing the control lines and this alternative may
eliminate or mitigate some or all of the issues identified above.
When the thermostat 208 makes a call for heat, one or more
components of the HVAC system will draw a current to service the
call for heat. For example, a relay (not shown) may be energized to
open the gas valve 128. Meanwhile, when a call for cool is made by
the thermostat 208, other components may draw a current--for
example, a relay may control the control module 156.
[0157] The current consumed by these various devices may be
different. For example, the current required to close a switch of
the control module 156 may be greater than the current required to
open the gas valve 128. An aggregate control line current may
therefore uniquely indicate various modes of operation. In FIG. 2A,
a current sensor 400 is shown associated with the control signals
exchanged between the thermostat 208 and the control module 112.
The current is received by the air handler monitor module 200.
[0158] In some HVAC systems, the difference in current between two
different modes may not be distinguishable with sufficient
accuracy. For these situations, additional sensing may be required.
For example, a sensor may be connected to a specific control line
to provide additional information so that the mode of operation can
be disambiguated.
[0159] In FIG. 4, example aggregate control line currents are shown
for five different operational modes of a particular HVAC system.
In an idle mode, none of the control lines are activated and an
aggregate current is 40 mA. In heating mode, a "W" control line,
which indicates a call for heat, results in an aggregate current
level of 60 mA. In a fan-only mode (for many thermostats, this is
when the fan setting is changed from auto to on) a "G" control line
is activated, resulting in an aggregate control line current of 110
mA.
[0160] When a call for heating is combined with a call for fan,
both control lines, "W" and "G" are activated, resulting in an
aggregate line current of 150 mA. When a call for cool is made,
control lines "Y" and "G" are activated with a resulting control
line current of 600 mA.
[0161] Note that for the heating mode, the "W" control line can be
activated by itself (without requiring activation of the "G" line).
This is because in some HVAC systems, such as used for FIG. 4, a
call for heat using the "W" control line automatically results in
the fan being activated. Meanwhile, in some HVAC systems, including
the example used for FIG. 4, the thermostat explicitly enables the
fan (using the "G" line) when making a call for cool.
[0162] Note that the control line currents for activation of the
"W" and "G" control lines independently do not add up to equal the
control line current when the "W" and "G" lines are activated
together. The inability to calculate the aggregate control line
current by linear superposition may be a common feature in HVAC
systems. For example, various components activated by the "W"
control line and the "G" control line may be common so that when
both the "W" and "G" control lines are activated, those common
components only contribute once to the aggregate control line
current.
[0163] In FIG. 5A, a more detailed view of the control signals for
an example HVAC system is shown. The thermostat 208 received power
over an "R" control line. In some implementations, a "C" control
line provides a current return path. The "C" control line is
omitted in various HVAC systems. A "G" line indicates a call for
the circulator blower, or fan. A "W" line indicates a call for
heating. A "Y" line indicates a call for cooling. The air handler
monitor module 200 monitors a current sensed by the current sensor
400. The current sensor 400 may measure the "R" line (as show in
FIG. 5A) or, in systems with a "C" line, may measure the "C" line
(not shown). The air handler monitor module 200 performs power-line
communications with the condensing unit 164 over a shared line,
such as over the "Y" line.
[0164] In systems without cooling, the "Y" line may be omitted and,
in systems without heating, the "W" line may be omitted. Further,
the "G" line may be omitted in systems where the fan is always
actuated automatically. Additional control lines that may be
present include a "Y2" line that indicates a second stage call for
cool. For example, the "Y2" line may indicate that the cooling
should be greater or lesser than for the "Y" line. An adjustment in
the amount of cooling may be accomplished by adjusting how many
compressors are used to provide cooling and/or by adjusting a
capacity of a compressor, such as with an unloader valve, a
variable speed drive, etc.
[0165] A "W2" line may provide for second stage heating, which in a
heat pump may include an electric secondary heating element. An
"O/B" line may be used to control a mode of the heat pump. The heat
pump systems may include additional control lines such as an EMR
(Energy Management Recovery) line or an auxiliary heat line.
Additional and alternative control lines may be present in various
other HVAC systems for which the monitoring system is used.
[0166] While the letter of each control line may indicate a
commonly-used color for the shielding of the wire, the actual
colors and labels of the control lines may differ in real world
systems. For this reason, the aggregate current may be a more
reliable indicator of mode than the state of individual,
unspecified control lines.
[0167] In FIG. 5B, a communicating thermostat 504 communicates with
a communicating control module 508 using some form of proprietary
communication such as a bidirectional digital interface. The
current sensor 400 may therefore measure input power to the
communicating control module 508. The measured current is received
by the air handler monitor module 200. The condensing unit 164 may
receive a single control signal from the communicating control
module 508. The air handler monitor module 200 may therefore use
that control line for power-line communications with the condensing
monitor module 204.
[0168] In FIG. 6, a flowchart shows example operation of a
monitoring system that determines HVAC operation mode based on
aggregate control line current. Control begins at 600, where a
current measurement is received corresponding to an aggregate
measure of control line currents. Control continues at 604 where
the received current is stored as an old current to which future
currents will be compared.
[0169] Control continues at 608 where a new current measurement is
received. Control continues at 612 where, if an absolute value of
the difference between the present current and the stored old
current is greater than a threshold, control transfers to 616;
otherwise, control transfers to 620. At 616, a timer is started at
a value of zero and the present current is stored as the old
current. Control then returns to 608.
[0170] The timer may be implemented to force a wait interval for
the aggregate current value to stabilize at a steady state value.
When the mode of the HVAC system changes, the value of the current
may initially take a period of time to stabilize. At 620, if the
timer is running, indicating that a large change in current had
occurred, implying a potential change in mode, control transfers to
624; otherwise, control returns to 608.
[0171] At 624, the timer was started and, therefore, the present
value of the timer is compared to a predetermined stable period of
time. If the timer exceeds that predetermined stable period,
control transfers to 628; otherwise, control returns to 608. At
628, the timer is stopped and at 632 the current, which is the most
recent value of the current and represents a steady state current,
is looked up in an operational table.
[0172] For example only, the operational table may be similar in
concept to that shown in FIG. 4. While FIG. 4 shows an individual
current value for each mode of operation, a range may be defined
around each current value in the table. This may take the form of a
percentage of the current value, or upper and lower limits may be
explicitly defined. For example only, each current level in the
table may be associated with an uncertainty of plus or minus ten
percent. Therefore, if the present value of the current is within
plus or minus ten percent of the value in the table, that table
entry may be assumed to be the correct table entry. Control
continues at 636, where if the value of the current corresponds to
a row in the operational table, control transfers to 640;
otherwise, control transfers to 644.
[0173] In various implementations, the operational table may be
predefined based on the identity of the HVAC system. The current
levels may be empirically determined and/or specified by the
manufacturer for a specific model and configuration of HVAC system.
This table may be stored in the monitoring system and accessed
based on an identifier associated with the installed HVAC system.
In other implementations, the operational table may be generated as
part of a calibration routine, which may be performed by an
installer of the monitoring system and/or a customer.
[0174] In various implementations, the thermostat may have a
predetermined calibration routine to allow this table to be
generated by cycling through each of the modes in a predetermined
order. In implementations where the operational table is
predefined, a determination that the current is not present in the
operational table signals an error. This may be reported to the
customer and/or an HVAC contractor as either the table needs to be
updated or a fault is causing the current to deviate from what is
predefined in the table.
[0175] In the example shown in FIG. 6, the table is not predefined,
and is instead constructed by the monitoring system. Therefore, at
644, control infers the mode corresponding to the current, which
has been determined to not be present in the operational table. For
example, this mode may be inferred based on temperature
measurements. If an outside ambient air temperature is above a
certain threshold, it is likely that a cooling mode has been
initiated. If the outside ambient temperature is below a certain
threshold, it is likely that a heating mode has been enabled.
[0176] Further, the supply air temperature may indicate whether
heating or cooling is being performed. And specifically, a
difference between the supply air temperature and the return air
temperature indicates whether heat is being added or removed to
circulating air. In situations where the supply air and return air
temperatures differ by only a small amount, an air flow sensor may
be able to determine whether the fan-only mode is engaged.
Meanwhile, when the supply air and return air temperatures differ
by only a small amount and there is an indication that minimal air
flow is occurring (such as from an airflow sensor), the system is
likely in an idle state.
[0177] Various other heuristics may be used, such as an inference
that a control line current that is more than ten times a lowest
measured current corresponds to a cooling mode. This is because the
contactor for an air conditioning compressor may draw significantly
more current than the components active in an idle system. The time
of year and geographical location of the HVAC system may inform the
mode inference. For example, a current level that is first seen in
October, in a colder climate, is likely to be related to a call for
heating.
[0178] In addition, system current data (i.e., the measured
currents from current sensors 216 and 264) can be used to infer the
operating mode of the HVAC system. Air conditioning, gas furnace,
electric heater, and fan-only modes may exhibit distinct system
current patterns. For example, air conditioning and fan-only modes
may have the same indoor current pattern (including just the blower
motor). However, the air conditioning mode will exhibit a
significant outdoor system current draw.
[0179] A gas furnace has a distinctive system current profile that
starts with inducer fan operation, followed by ignition, then a
purging (or waiting) period to allow the heat exchanger to heat up,
then blower operation. Meanwhile, an electric heater generally
draws significantly greater indoor system current than does a
gas-powered furnace and also does not have the initial steps
(inducer fan, ignition, etc.) associated with a gas furnace.
[0180] After the mode is inferred, control continues at 648, where
the current level and mode are added to the operational table.
Control then continues at 640. At 640, control reports the
operational mode that is determined from the table. The reported
operational mode may be reflected on the contractor portal 328 or
the customer portal 332 of the remote monitoring system 304.
[0181] In addition, the table may be updated with information
regarding how the present current differs from the stored current
level. For example, if, over time, all of the current levels
associated with the heating mode are five percent higher than the
nominal current level stored in the operational table, the
operational table may be adjusted so that the measured current
falls in the middle of the range of the stored current level. This
may allow for small drifts in current as the HVAC system ages.
[0182] At 652, control determines a system condition of the HVAC
system. The system condition may include detections of various
faults, including those described above. The system condition may
include predictions of various faults, as described above. The
system condition may also include a reduction in performance or
efficiency--while such a condition may also be characterized as a
fault, it may be treated separately from a fault when there is no
corresponding system component that has actually failed. Control
then returns to 604.
[0183] The foregoing description is merely illustrative in nature
and is in no way intended to limit the disclosure, its application,
or uses. The broad teachings of the disclosure can be implemented
in a variety of forms. Therefore, while this disclosure includes
particular examples, the true scope of the disclosure should not be
so limited since other modifications will become apparent upon a
study of the drawings, the specification, and the following claims.
As used herein, the phrase at least one of A, B, and C should be
construed to mean a logical (A OR B OR C), using a non-exclusive
logical OR, and should not be construed to mean "at least one of A,
at least one of B, and at least one of C." It should be understood
that one or more steps within a method may be executed in different
order (or concurrently) without altering the principles of the
present disclosure.
[0184] In this application, including the definitions below, the
term module may be replaced with the term circuit. The term module
may refer to, be part of, or include an Application Specific
Integrated Circuit (ASIC); a digital, analog, or mixed
analog/digital discrete circuit; a digital, analog, or mixed
analog/digital integrated circuit; a combinational logic circuit; a
field programmable gate array (FPGA); a processor (shared,
dedicated, or group) that executes code; memory (shared, dedicated,
or group) that stores code executed by a processor; other suitable
hardware components that provide the described functionality; or a
combination of some or all of the above, such as in a
system-on-chip.
[0185] The term code, as used above, may include software,
firmware, and/or microcode, and may refer to programs, routines,
functions, classes, and/or objects. The term shared processor
encompasses a single processor that executes some or all code from
multiple modules. The term group processor encompasses a processor
that, in combination with additional processors, executes some or
all code from one or more modules. The term shared memory
encompasses a single memory that stores some or all code from
multiple modules. The term group memory encompasses a memory that,
in combination with additional memories, stores some or all code
from one or more modules.
[0186] The term memory is a subset of the term computer-readable
medium. The term computer-readable medium, as used herein, does not
encompass transitory electrical or electromagnetic signals
propagating through a medium (such as on a carrier wave); the term
computer-readable medium may therefore be considered tangible and
non-transitory. Non-limiting examples of a non-transitory, tangible
computer-readable medium include nonvolatile memory (such as flash
memory), volatile memory (such as static random access memory and
dynamic random access memory), magnetic storage (such as magnetic
tape or hard disk drive), and optical storage.
[0187] The apparatuses and methods described in this application
may be partially or fully implemented by one or more computer
programs executed by one or more processors. The computer programs
include processor-executable instructions that are stored on at
least one non-transitory, tangible computer-readable medium. The
computer programs may also include and/or rely on stored data.
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